yinqiwu/qPID

Open PID Controller for embedded systems

qPID Digital PID controller library

Introduction

This library is a digital Proportional-Integrative-Derivative digital controller designed for embedded systems to interact with real systems.

Principle of work and definitions

Block Diagram

Detailed information

Full mathematical description and testing results of this libarary can be found (in spanish) in kharsansky-quadrotor-control-thesis.

Usage example

#include "qPIDs.h"

float setPoint = 0.0;
float sensor = 0.0;
float output = 0.0;


// Example usage for the qPID library for controlling the speed of a simle motor
// The idea is to control the speed of the motor by varing the voltage applied via PWM

float readSensor(void);			// A function that reads the motor speed from a sensor
float readSetPoint(void);		// A function that reads the desired speed from a potentiometer
void setActuator(float);				// A function that sets the PWM output for controlling the motor

void example(void){

	// Declare de new object
	qPID controller;
	
	// Configure settings
	controller.AntiWindup = ENABLED;
	controller.Bumpless = ENABLED;
	
	// Set mode to auotmatic (otherwise it will be in manual mode)
	controller.Mode = AUTOMATIC;
	
	// Configure de output limits for clamping
	controller.OutputMax = 1.0;
	controller.OutputMin = -1.0;
	
	// Set the rate at the PID will run in seconds
	controller.Ts = 0.005; 
	
	// More settings
	controller.b = 1.0;
	controller.c = 1.0;
	
	// Init de controller
	qPID_Init(&controller);

	// Set the tunning constants	
	controller.K = 0.5;
	controller.Ti = 1/0.02;
	controller.Td = 0.0;
	controller.Nd = 4.0;
	
	while (1){
		sensor = readSensor();				// update the process variable
		setPoint = readSetPoint(); 			// update the user desired value
		
		// Update the PID and get the new output
		output = qPID_Process(&controller, setPoint, sensor);
		
		setActuator(output);				// update the actuator input
	}
	
}